Embodiments of the present invention relate generally to current transformers, and more particularly to a high sensitivity differential current transformer for insulation health monitoring.
Current transformers are devices used to scale large primary currents to smaller, easy to measure, secondary currents. Generally, in the current transformers, the ratio of the windings determines the relation between input and output currents. Furthermore, current transformers of various shapes and sizes may be used as interfacing solutions between high currents and instrumentation devices.
Moreover, current transformers are also extensively used for measuring current and monitoring the operation of a power grid. By way of example, a differential current transformer may be used for measurement of leakage current in an insulation monitoring system. Also, as will be appreciated, there are various types of faults that may develop in industrial motors during operation. A majority of these faults in large motors may be related to stator-winding insulation. It is therefore desirable to monitor the condition of stator insulation in order to safeguard these motors. Currently, offline tests are available to determine the health of stator insulation in a motor. Unfortunately, these tests require an outage of the motor from service. For example, partial discharge analysis is one technique that may be used to measure online or offline the insulation corona discharge activity on large motor windings. Differential current transformers have been used to protect a motor from catastrophic damage only after a failure has already occurred. However, these techniques fail to facilitate assessment of the health of stator insulation while the motor is operational.
It is therefore desirable to develop a monitoring system that is capable of assessing the health of stator insulation while the motor is operational. More particularly, it is desirable to develop a monitoring system that facilitates online assessment of the health of stator insulation.